GEOFF BENNETT: The U.S.

says it's closely monitoring a potential case of pneumonic plague in Russia after a laboratory worker who studied the disease fell ill and died.

Russian authorities say the worker died from pneumonia of an unknown cause and insist there is no cause for alarm.

But Russian officials have also imposed quarantines and other anti-epidemic measures at several medical facilities in Siberia, with at least 200 people now under medical observation.

There is no confirmation the worker contracted plague, but she worked at a research facility that studies the disease, raising questions about what she may have been exposed to and whether there is any risk of a wider outbreak.

President Trump was asked about those concerns as he left the White House this afternoon.

QUESTION: What is the U.S.

going to do about the risk of pneumonic plague coming from Russia?

DONALD TRUMP, President of the United States: Well, we're looking at it very strongly.

We just heard about it.

And they call it pneumonia.

And pneumonia, years ago, you could treat pneumonia easier.

The microbes and the germs have gotten stronger, disproportionately, but we will help them.

GEOFF BENNETT: For more, we're joined now by investigative journalist Annie Jacobsen, author of "Biological War: A Scenario."

Annie, thank you for being with us.

You wrote an entire book about a biological crisis involving pneumonic plague.

When this story first broke, what did you make of it?

ANNIE JACOBSEN, Author, "Biological War: A Scenario": I mean, I was sort of shocked-not shocked.

Look, the idea about a lab accident causing an epidemic or a pandemic is based on real facts.

It's also based on experience.

So I think what's kind of alarming is not just what happened, but the fact that now you have a situation where you have the Russian Federation working very hard to close down all information about this.

GEOFF BENNETT: So, separate what we know from what we don't.

What has actually been established about this worker's illness and death and what remains speculative?

ANNIE JACOBSEN: Well, she's dead.

That's for sure.

What we don't know is what's going on with the 200 other people who are allegedly quarantined, or any of the other people in the five facilities that are also under quarantine.

I think, once we have some information about that, it'll be much clearer about if this is a transmissible variant, if other people are dying.

But, again, because we're getting nothing from the Russian Federation, after, by the way, a very strong initial clamp down - - FSB was involved.

That's no small thing.

GEOFF BENNETT: Is there anything about the response itself, the quarantines, the medical observation, the involvement of Russia's top public health officials, that tell you something about what Russian authorities might be worried about?

ANNIE JACOBSEN: Well, what they're worried about is that there -- this is an Anti-Plague Institute, so they're supposed to be studying medical countermeasures to plague, like vaccines, antibiotics.

But this particular institute, we know from Soviet defector scientists, was used for biological weapons engineering during their illegal program.

We also know the State Department believes that that illegal biological weapons program has continued.

And so what they're really worried about is eyes on this facility, both from the intelligence community here in the United States and the military community, looking at that facility and being like, what is going on?

I mean, look, the facility is -- has six-foot-high fences around it.

It's got concertina wire on top of that.

It's controlled in and out.

The idea that this worker broke a test tube and suddenly contracted pneumonic plague, which is inhalation plague, that does not entirely add up for somebody like me.

What I would be most concerned about is that they're kind of -- one idea is that they could be milling the pathogen, making it aerosolized.

That gets you right into the world of biological weapons engineering.

GEOFF BENNETT: What power, if any, does the WHO, the World Health Organization, have here, or does it depend entirely on Russia's willingness to cooperate?

ANNIE JACOBSEN: The latter.

It depends entirely on Russia's ability or willingness to cooperate.

Moscow shut down its WHO office during the Ukraine war, the beginning of it.

So it is my understanding that the WHO has reached out to Russian health officials and asked for information and that they have not gotten any.

GEOFF BENNETT: Is the pneumonic plague as transmissible as, say, COVID?

ANNIE JACOBSEN: Well, that's the question.

I mean, Mother Nature's pneumonic plague, no.

COVID was airborne.

It was aerosolized.

You could catch it in the air if you were in the room with someone that had COVID.

Pneumonic plague, again, Mother Nature's variant, that is pneumonic plague in the wild, is what's called droplet-transmissible.

So, excuse the graphics here, but you have to actually like kind of spit on someone or cough loudly at them.

And you would also have to be very sick to be doing that, which would make the likelihood of your close proximity without some kind of PPE unusual.

But if genetic modifications are going on, all bets are off as to how transmissible it could potentially be.

GEOFF BENNETT: And, of course, COVID exposed just how costly a lack of transparency and cooperation among governments can be in the early stages of an outbreak.

Do we have any better mechanisms today of, I guess, in this case it would be forcing countries to be transparent and cooperate to stem an outbreak before it starts?

ANNIE JACOBSEN: And that is, of course, the most important question and the most important point, by all means.

I mean, transparency is going to be the way forward or should be the way forward, because the more we know about an outbreak, the more countries can prepare to mitigate the threat, in essence.

But, again, Russia is absolutely - - not only are they not saying anything.

They're actually backtracking, and they also have really clamped down apparently on the journalists who were originally doing great reporting on the ground about quarantines.

Those people have gone completely silent.

GEOFF BENNETT: Journalist and author Annie Jacobsen.

The latest book is "Biological War: A Scenario."

Thank you for your sharing your insights and reporting with us.

We appreciate it.

ANNIE JACOBSEN: Thank you for having me.